Conversion of propylene and isobutylene to allene and methylacetylene



Feb. 16, 1960 2,925,451

M. J. HOGSED CONVERSION OF PROPYLENE AND ISOBUTYLENE TO ALLENE AND METHYLACETYLENE Filed March 20, 1 95'7 MILTON J. HOGSED BY MAM@ ATTORNEY Ice? l2,925,451,

coNvnRsIoN oF PRoPYLENE rsonrYL- ENE To ALLENE AND MEIHYLACETYLENE vMilam Innes Hogsed, .Wilmingtompelgssigndr fn E. I. du Pont'dNeiolrs andCompany, Wilmington, Del.,

.La corporation'of'Delaware 'i Y Application March zo, 1957, serial No. 647,3'5s A :wm 1,1- zcew g Thisinvention "relates to ari improved'method forl preparing allene, andmore particularly to an improved'. n'iethod fo rconverting isvobutylene and propylene to alieneV and niethylacetyiene. u y

hAllene, the simplest diene hydrocarbon, offers special opportunities lfor the synthesis'ofa wide varietyjof Parenteel-en 16, Y1960 'A'tonisv of the Vequipriient illustrated may be employed without departing from the scope of the 'pesetinventiom In operation, the olefin, isobutylene or propylene, is

passed over a heatd'iil'ment at afcntact vtime of less thannOOl secondandunder apressure below V100 mm.

Axtstart-up the system is Vushedwitl hitrogen'rwhile the iilanent'is heated tothedesired temperature. After the desired temperature has been attained, nitrogen ow is discontinued and the owofolefin is started. After pre- 10 determined volume of the Aoleiinrhas, been put throughv the reactor, the system is flushed with nitrogen. Products j; are. collectedin a'trap cooled to 196 C. with liquid nitrogen.v The product in thetrap is then transferred to' ,receiver byhleedingY into an kevacuated container and 15 stored.

. The time of reaction` is calculated by determining contactstime; which is defined as the volume of thereaction zone divided vby. the `throughput volume at reaction temperature. yThr.",'.throughp1.itv Vat reaction temperature isA 20 calculated by multiplying the volume of gas at standard chemicalsbecauvse of its highly reactiveknature. Therej are a numbergofpublish'edmethods for its preparation,

some of which are primarily of academic interest. One,v Y

7103,'-i'ssed to J. Happelgand-"C.J.l Marsel Vol1` September 18, 1956) is the vdernethanationof isobutylene at80 0' 900='C.='in' the presence of 807-90 molepercent of steam.,

This pr'ocedurepro'duces' one mole ofmethane foreveryj contacting propylene i op tylenejatf-aj pressure fbelow" 1(10. .nini-. imercury` vwith afmetal filament heated tQ at least conditions-by [1-|-T K. 0.003661]. 'Space velocity,` Vsg'isgthe hourly throughput volume at standard conditionsdivided bythe reaction zone volume. v Y

` '"lqseoose'conds ,asX-ro ef drawing:

40 obtained 'by the; usefof .ay heated metaly filament "arejcornY-V Y The attached drivirigYFig. `I) illustrates in simple y obtained byz conventional :.'heating methods.'

i Isobutylene Combined Run Temp.,y Contact 'Time Consump- A-i-MA b AIMA b Y O. per sec. tion, Yield Percent Quartz Furnace l f. y, 900 0. 04 13.4 vIsobutylene alone over Pt wire at 32-35 mm- 1, 015 0. 001 to 0.01 54. 0 Chromesteel Furnace.- 850V 0.14 11.8 j `Isobutylenealone over Pt wire at k970 70. 001 to 0. 01 25. 0

Quartz Furnace t -V. 950V Y I 0. 05 23.8 Y D0 875 0. 14 24.0

; l L. A; Wall vDoctora] Dissertation, Catholic University of America (1946).

b Allenelmetliacetylene. i f

port.

ene at controlled ratesto a pyrolysis zone,means vfor Y contacting the olefin-with 'a metal filament heated by-i11- duction or resistance to current, means for condensing the product and means for maintaining and controlling the pressure in the reaction system.' Various modiicae These are estimates because ofthe eompllcetedshape otthe coils ofrPt wire suspendedtrom tungesten sup' 0 Usingithe equipment illustrated the attached draw- Y .1ng, propylene was pyrolyzed at pressures of 40-80 mm.

Vand temperatures yof 950l to 1400 C. over platinum '7. gauze, and over Nichrome 2 helices heated by resistance 1 Coetlicient of expansion at 86 C. Y Y An 85% Ni, 12% Fe, 11% or, and 2% Mn alloy.

v (F1g.- I); isobutylene: lwas passedqthrough the wettest Y. meter,Y then through thef l n'eedleyalve'that controlledthe 'owvrate.` 1" Afterleaving-fy `35 the pyrolysis chamber, the .pyrolizate was condensed inaffliquid l.nitrogen--cooled trappflhe significantimpfove- -ments ein fyields'.r achieved by low pressure pyrolysis l' over ahnt-,platinum wire atrcomacttimefof lessp'than 0.01 'second KAare shown .in the; table below, where th'e'valuesl- The pyrolysis conditions and results areArr The process of this invention is an 'advantage over t CUII'BII. summarized in the table which follows; prior methods by maklng 1t possible to convert isobutylene Combined Liquid NrCooled Condensate Contact Propylene Yield Composition Analysis Metal Packing Time Maximum Consumpof Allene per sec. Temp., C. tion, And MeAe,

percent percent Allene, MeAc, Ethylene, g

percent percent percent Nichrome O. 002 950 to above 17 28 1. 6 1. 4 6

M.P. ot' Nlchrome. Do 0. 001 36 23 3. 7 3. 8 12 Pt Gauze 0. 0002 1,010 7 25 1.0 0.6 2

0.0005 1,040 16 25 2.3 1.3 4fY 0. 0002 1,400 40 17 3l 3. 2 10 Example III Propylene was pyrolyzed at 50 mm. in the manner described above, using coiled platinum` wire: heated to over 1000o C. by resistance to current from a transformer. The contact time was estamiated as being less than 0.01 sec. Allene. and methylacetylene were produced in a combined yield of 26% at a propylene consumption of 23%. Yields were negligible at pressures above 100 mm. under similar temperature conditions and contact times.

The highly improved yields obtained by the process of the present invention primarily result from the use of contact times below 0.01 second, as shown by the examples.

Although in the examples platinum and Nichrome have been used, it is to be understood that this is only for convenience and that there is nothing critical about these materials. vIn their place, there can be used other metals or alloys of high resistivity in the form of gauze or filament.

The pyrolysis is effected at temperatures in the range of 9001600f1 C. at contact times of 0.001 to 0.01 sec. Very short contact times are essential to obtain the best balance of olefin consumption-with product yield.

The isobutylene and propylene employed can be of reagent or commercial quality and canfbeof .petroleum origin or otherwise prepared. Isobutylene and propylene not converted by one: pass through` the reaction system may be continuously recycled. y Y

The process of this invention is operated under reduced pressures, i.e., pressure of less than 0.13 atmosphere and. preferably below 0.08 atmosphere. This has the' practical advantage of markedly increasing the throughput less than 0.0.1 second, cooling the resultingproducts, and

separating allene and methylacetylene from said reaction products.

2. A process for Ithe preparation of allene and methylacetylene which comprises passing propylene at Va pressure below 0.08 atmosphere over a metallic iilament Yof high resistivity heated to a temperature of 900 C. to 1600 C. at a contact time'of 0.0002 to 0.01 second, cooling the Y.resulting products, and separating. allene and methyl,-

acetylene from saidreaction products.

3.` A process for the preparation of allene and methyl;- acetylene which comprises Vpassing isobutylene at a pressure-below 0.08 atmosphere over.y ametallic lament of Y Yhigh resistivity'v heated to a ltemperature-,of 9009 C. to Y1600"C. at a contact time of- 0.0002 to 0.01 second, coolcapacity of the equipment and thus makes it possible to utilize itat maximum etciency. By avoiding the use of steam, costs are reduced and the recovery'of the desired i allene is simplified.

ingthe Yresulting products and separatingallene :and:v methylacetylenel from said reactionY productsl in` a ratio of allene to methylacetylene of greater than one.'

References Cited in thefiIe-ofv. this Apatent UNITED STATES PATENTS.

2,429,566 Rice ocr. 21, 1947 2,543,005 Evans Feb. 27,1951.` 2,543,743 Evans 1 Feb. 27,l 1951 Auerbach .)J'uly 25', 1939 UNITED STATES PTENT OFFICE' CERTIFICATE oF 4CORRECTION lPatent No.. 2,925,451 February 16, 1960 Milton Jones Hogsed It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction and that the said Letters Patent "should readI as corrected below.

Column 2, line 7l, Example Il, in the first footnote, for "800 C." read 800o C. column 4, line l, for I"ao1vantage",

read advance -v-.

\S'i'gned and sealed this 2nd day of August 1960.

Attest: u KARL H.- AXLINE ROBERT C. WATSON Commissioner of Patents Attesting Ofcer 

1. A PROCESS FOR THE PREPARATION OF ALLENE AND METHYLACETYLENE WHICH COMPRISES PASSING AN OLEFIN OF THE CLASS CONSISTING OF ISOBUTYLENE AND PROPYLENE AT A PRESSURE BELOW 100 MM. MERCURY OVER A METALLIC FILAMENT OF HIGH RESISTIVITY HEATED TO AT LEAST 900* C. AT A CONTACT TIME OF 